CoAP Protocol Negotiation
draft-silverajan-core-coap-protocol-negotiation-00

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CoRE Working Group                                         B. Silverajan
Internet-Draft                          Tampere University of Technology
Intended status: Informational                             March 9, 2015
Expires: September 10, 2015

                       CoAP Protocol Negotiation
           draft-silverajan-core-coap-protocol-negotiation-00

Abstract

   CoAP has been standardised as an application level REST-based
   protocol.  This document introduces a way for CoAP clients and
   servers to interact with resources by agreeing upon alternate
   locations as well as transport and protocol configurations.

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   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on September 10, 2015.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  New Link Attribute and Relation types . . . . . . . . . . . .   3
   3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Constrained Application Protocol (CoAP) [RFC7252] provides a
   lightweight request-response messaging mechanism for retrieving and
   manipulating resources identified by Uniform Resource Identifiers
   (URIs).  However URIs have a twofold purpose in CoAP: In addition to
   identifying resources, URIs are also used as locators for origin
   servers, proxies and endpoints delivering resource representations to
   clients.  Should an origin server wish to serve a resource over
   multiple transports, a single CoAP URI cannot be used to express the
   identity of the resource independently of alternate underlying
   transports or protocol configurations.  Similarly, if the server
   wishes to serve representations of the resource from a different
   endpoint and path, the URI mechanism is incapable of capturing the
   relationship between these alternate representations or locations.

   This draft proposes a new link format attribute as well as a new link
   relation type that together enable an origin server to serve a
   resource from other protocol configuratons or endpoints.  CoAP
   clients then interact with an origin server's CoRE resource discovery
   interface to obtain a set of links describing alternate locations of
   resources.

   This is useful in the following cases:

   1.  CoAP clients interacting with Type T1 or T2 CoAP origin servers
       (see Section 3 of
       [I-D.silverajan-core-coap-alternative-transports]) either before
       or during an ongoing transaction to communicate using CoAP over a
       different protocol configuration or alternative transport.

   2.  Avoiding URI aliases [WWWArchv1], where a single resource is
       represented with multiple URIs, without describing relations
       among the alternate representations.

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   3.  Allowing intermediate nodes such as CoAP-based proxies to
       intelligently cache and respond to CoAP clients with the same
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